res.status() | DevNotes

res.status() sets the HTTP status code for the response and returns res, so it chains neatly with res.send() or res.json().

const express = require("express");
const app = express();

app.get("/products/:id", (req, res) => {
    const found = req.params.id === "1";
    if (!found) {
        return res.status(404).json({ error: "Product not found" });
    }
    res.status(200).json({ id: 1, name: "Wireless Mouse" });
});

app.listen(4600, () => console.log("Listening on 4600"));

Common uses

Signaling success (200, 201) or failure (400, 404, 500) explicitly.
Building consistent, predictable REST API responses.
Pairing with res.json()/res.send() for a complete response.